Brain Monitoring During PEEP-Based Respiratory Therapy in Critically Ill Patients

Mechanical ventilation is commonly used in critically ill patients with acute brain injury. Positive end-expiratory pressure (PEEP) and lung recruitment maneuvers are important ventilator strategies for improving oxygenation, but they may also influence cerebral blood flow, systemic hemodynamics, carbon dioxide levels, and brain electrical activity. The effects of PEEP-related ventilator changes on cortical function in neurocritical care patients remain insufficiently understood. This prospective observational physiological study will evaluate changes in brain electrical activity and cerebral blood flow during clinically indicated lung recruitment maneuvers and PEEP adjustments in mechanically ventilated neurocritical care patients. Multimodal monitoring will include electroencephalography (EEG), transcranial Doppler ultrasound, invasive arterial blood pressure, end-tidal carbon dioxide, and routine clinical variables. EEG-derived measures, including delta power ratio and related frequency-domain indicators, will be used to describe cortical activity. Cerebral blood flow velocity and low-frequency neurovascular coupling measures will be explored as secondary physiological outcomes. The study will examine whether PEEP-related changes are associated with alterations in EEG activity, cerebral blood flow, and neurovascular coupling, and whether these responses differ according to clinical status. The results may help improve understanding of brain-lung interactions during mechanical ventilation and inform future studies on individualized ventilation strategies in neurocritical care.

Inclusion Criteria: * Age ≥18 years. * Admission to the neurocritical care unit with acute brain injury requiring intensive care management. * Receiving invasive mechanical ventilation. * Undergoing clinically indicated recruitment maneuvers and positive end-expiratory pressure (PEEP) adjustments. * Availability of an adequate temporal acoustic window for transcranial Doppler monitoring. * Written informed consent obtained from the participant or a legally authorized representative. Exclusion Criteria: * Pregnancy. * Hemodynamic instability precluding recruitment maneuvers or PEEP adjustments. * Severe cardiac dysfunction judged by the treating physician to contraindicate study procedures. * Inability to obtain adequate transcranial Doppler signals. * Conditions preventing EEG monitoring, including extensive scalp injury or dressings that preclude electrode placement. * Withdrawal of informed consent.